Perscitus Biosciences, LLC, is developing a novel protein proximity assay with broad applications to the pharmaceutical and biomedical community. Currently, there are no satisfactory approaches for examining large protein complexes in an intact cell and identifying associated proteins that may be important in discerning function. Researchers determine from microarray and other studies that a protein may be implicated in a disease process, but are unable to determine what the function of that protein is within the cell. The protein proximity technology being developed by Perscitus allows for the selective tagging of proteins within a limited radius of the protein of interest. The approach utilizes an active oxygen species, singlet oxygen, created photochemically, that is capable of only limited diffusion from its site of creation. This diffusion distance closely approximates the size of a multimeric protein complex. Singlet oxygen reacts with neighboring proteins, creating a carbonyl group that can be utilized for protein detection, identification and purification. The approach is tunable and precisely initiated at the time of illumination. We are proposing a focused investigation of this protein proximity assay to demonstrate proof of concept that can be used in marketing this approach to pharmaceutical companies. We will initially examine the protein MDM2 because of its broad importance to cancer biology, and the existence of a number of known binding partners that will serve as positive controls in our proof of concept studies. The simplicity and scalability of this approach should make for a powerful proteomic method that will have broad applicability to biomedical and pharmaceutical investigators. [unreadable] [unreadable] [unreadable]